The invention relates to a method for producing a one- or multidimensional detector array for detecting electromagnetic radiation, in particular for detecting X-rays.
For computer tomograph apparatuses or for other apparatuses in which X-rays or other high-energy radiation has to be detected using detectors, luminescent or scintillator materials are used which transfer the X-rays or high-energy radiation into other electromagnetic radiation whose spectral region is accessible to the human eye or a photoelectric receiver. Such a scintillator material, a so-called UFC ceramic (Ultra-Fast Ceramic), is described for example in U.S. Pat. No. 5,296,163.
Detectors which are structured in at least one direction are required for obtaining a spatial resolution of the X-ray signal.
For faster image processing and for reasons of improved utilization of the pencil of rays radiated by an X-ray source, it is also known to design an X-ray detector in such a way that it is structured along two mutually perpendicular axes, thereby forming a two-dimensional detector array. Such two-dimensional arrays are disclosed for example in U.S. Pat. No. 5,440,129 and EP 0 819 406 A1.
Producing one- or multidimensional detector arrays with luminescent or scintillation material is costly and causes a high manufacturing outlay, in particular in the case of production in high numbers.
The invention is based on the object of specifying a production method for detector arrays for detecting electromagnetic radiation which makes it possible to produce such detector arrays with a low outlay.
With a method of the type mentioned in the introduction, this object is achieved according to the invention by virtue of the fact that
a) a layer composite is produced, which has a sensor layer with a material sensitive to the radiation, and a carrier layer, and
b) that in order to subdivide the sensor layer into individual elements isolated from one anotherxe2x80x94separating spaces are introduced into the sensor layer proceeding from that side of the layer composite which is opposite to the carrier layer, by material being removed.
The method can advantageously be carried out in a simple manner in terms of manufacturing technology. The separating spaces can be produced as channels, troughs or grooves, in particular projecting into the carrier layer. They can be introduced by a machine in parallel with one another in rapidly succeeding work steps. It is not necessary to handle individual sensor elements. The separating spaces are preferably introduced by sawing, milling or erosion.
Preferably, the radiation-sensitive material used is a luminescent or scintillation material which is sensitive to X-rays, in particular. This makes it possible to produce an X-ray detector in a simple manner.
According to a preferred refinement, the carrier layer contains a reflector material which reflects the radiation emitted by the luminescent or scintillation material.
According to another preferred refinement, a reflector material is filled, in particular cast, into the separating spaces. It is possible, in particular, in an advantageous manner, for all the separating spaces to be filled in a single work step. The filled-in reflector material is in particularxe2x80x94like the material of the carrier layerxe2x80x94a material which reflects the radiation emitted by the luminescent or scintillation material. In this way, the elements formed by the separating spaces are optically isolated from one another and from the surroundings toward four sides and toward the rear side closed off by the carrier layer. This means that ambient light from five sides cannot penetrate into an element of the sensor layer, and that, on the other hand, luminescence light generated by the luminescent or scintillation material in the element is reflected back from five sides and is collected at the sole side remaining open, for example for coupling a photodetector. Moreover, crosstalk between the individual elements of the sensor layer is avoided by virtue of the separating spaces filled with reflector material.
According to a particularly preferred refinement, the separating spaces are introduced, in particular as mutually crossing grooves, in such a way as to form a structure of elements arranged in a matrix-like manner.
Such a matrix-like structure can be used for producing a two-dimensional detector array, the elements of the structure being used as sensor elements. For this purpose, each of the elements may be brought into contact, on its side which faces away from the carrier layer and represents the sole side that is still open when said reflector material is provided, in each case with a photoelectric receiver in particular with a photodiode. Each combination of a sensor element with a photoelectric receiver then forms a detector element which, on the output side, can be connected to an evaluation unit.
The method according to the invention also advantageously makes it possible to produce a plurality of two-dimensional detector arrays in one work step. For this purpose, the structure of elements arranged in a matrix-like manner is manufactured in an appropriate size and then broken down into a plurality of matrix-like substructures.
According to an especially preferred embodiment, the method is employed for producing a plurality of one-dimensional detector arrays. For this purpose, the structure of elements arranged in a matrix-like manner is broken down, for example sawn, into row portions or into column portions.
The row portions or column portions for producing one-dimensional detector arrays can be obtained in a number of variants:
According to a first variant, the row portions or the column portions are formed by the structure of elements arranged in a matrix-like manner being divided along a plurality of mutually parallel first separating planes which run only through the separating spaces. In this case, the separation along the separating spaces is preferably carried out in such a way that, on both sides of each separating plane, the amount of reflector material that remains is as much as is needed to shield the adjacent elements of the sensor layer.
Only when divisions are implemented along such first separating planes can the elements of the resulting column portions or row portions be used as sensor elements. They may be brought into contact, on their side which faces away from the carrier layer and is not covered by the reflector material, in each case with a photoelectric receiver, in particular with a photodiode.
According to a second variant, row portions or column portions are formed by the structure of elements arranged in a matrix-like manner being divided along a plurality of mutually parallel second separating planes which in each case run between two first separating planes and in each case separate a row or a column into a plurality of parallel row portions or column portions, respectively. The second separating planes preferably run parallel to the first separating planes.
Whereas in the first variant n row portions, for example, can be generated if the matrix-like structure has n rows, in the second variant 2n row portions are produced from a structure having n rows. In the second variant, it is expedient, therefore, for the height of the rows (in the column direction) to be chosen to be correspondingly larger.
Preferably, in the second variant, before the process of splitting into row portions or into column portions, a covering layer, which preferably contains a reflector material, is applied on that side of the layer composite which is opposite to the carrier layer.
In this way, the sensor elements produced in accordance with the second variant are also shielded toward five spatial directions.
In the second variant, an open, unshielded side remains in the sensor elements, in particular on the second separating planes. The row portions or column portions produced according to the second variant are therefore preferably used with their elements as sensor elements by being brought into contact, on the second separating planes, in each case with a photoelectric receiver, in particular with a photodiode.
The radiation-sensitive material is preferably a luminescent ceramic, in particular and xe2x80x9cUltra-Fast Ceramicxe2x80x9d (UFC ceramic), for example one as described in U.S. Pat. No. 5,296,163, column 6, line 50, to column 8, line 32.
A diffusely reflecting or scattering material, preferably with a white color, e.g. an epoxy resin filled with titanium oxide, is preferably used for the constituents of the detector array produced that are provided with reflector material.
The detector array produced can advantageously be used for detecting X-rays in a computer tomograph. In the method variant for producing a two-dimensional detector array, the rows and columns of the produced structure of elements arranged in a matrix-like manner are then adapted in terms of their number, width and order to the so-called z-direction or (xcfx86-direction of the computer tomograph.